webrtc选择摄像头麦克风

最近在阅读webrtc的使用方法，这里将对其做一个总结

1、main.js文件

核心代码：

 if (window.stream) {
    window.stream.getTracks().forEach(track => {
      track.stop();
    });
  }
  const audioSource = audioInputSelect.value;
  const videoSource = videoSelect.value;
  const constraints = {
    audio: {deviceId: audioSource ? {exact: audioSource} : undefined},
    video: {deviceId: videoSource ? {exact: videoSource} : undefined}
  };
  navigator.mediaDevices.getUserMedia(constraints).then(gotStream).then(gotDevices).catch(handleError);

/*
*  Copyright (c) 2015 The WebRTC project authors. All Rights Reserved.
*
*  Use of this source code is governed by a BSD-style license
*  that can be found in the LICENSE file in the root of the source
*  tree.
*/

'use strict';

const videoElement = document.querySelector('video');
const audioInputSelect = document.querySelector('select#audioSource');
const audioOutputSelect = document.querySelector('select#audioOutput');
const videoSelect = document.querySelector('select#videoSource');
const selectors = [audioInputSelect, audioOutputSelect, videoSelect];

audioOutputSelect.disabled = !('sinkId' in HTMLMediaElement.prototype);

function gotDevices(deviceInfos) {
  // Handles being called several times to update labels. Preserve values.
  const values = selectors.map(select => select.value);
  selectors.forEach(select => {
    while (select.firstChild) {
      select.removeChild(select.firstChild);
    }
  });
  for (let i = 0; i !== deviceInfos.length; ++i) {
    const deviceInfo = deviceInfos[i];
    const option = document.createElement('option');
    option.value = deviceInfo.deviceId;
    if (deviceInfo.kind === 'audioinput') {
      option.text = deviceInfo.label || `microphone ${audioInputSelect.length + 1}`;
      audioInputSelect.appendChild(option);
    } else if (deviceInfo.kind === 'audiooutput') {
      option.text = deviceInfo.label || `speaker ${audioOutputSelect.length + 1}`;
      audioOutputSelect.appendChild(option);
    } else if (deviceInfo.kind === 'videoinput') {
      option.text = deviceInfo.label || `camera ${videoSelect.length + 1}`;
      videoSelect.appendChild(option);
    } else {
      console.log('Some other kind of source/device: ', deviceInfo);
    }
  }
  selectors.forEach((select, selectorIndex) => {
    if (Array.prototype.slice.call(select.childNodes).some(n => n.value === values[selectorIndex])) {
      select.value = values[selectorIndex];
    }
  });
}

navigator.mediaDevices.enumerateDevices().then(gotDevices).catch(handleError);

// Attach audio output device to video element using device/sink ID.
function attachSinkId(element, sinkId) {
  if (typeof element.sinkId !== 'undefined') {
    element.setSinkId(sinkId)
      .then(() => {
        console.log(`Success, audio output device attached: ${sinkId}`);
      })
      .catch(error => {
        let errorMessage = error;
        if (error.name === 'SecurityError') {
          errorMessage = `You need to use HTTPS for selecting audio output device: ${error}`;
        }
        console.error(errorMessage);
        // Jump back to first output device in the list as it's the default.
        audioOutputSelect.selectedIndex = 0;
      });
  } else {
    console.warn('Browser does not support output device selection.');
  }
}

function changeAudioDestination() {
  const audioDestination = audioOutputSelect.value;
  attachSinkId(videoElement, audioDestination);
}

function gotStream(stream) {
  window.stream = stream; // make stream available to console
  videoElement.srcObject = stream;
  // Refresh button list in case labels have become available
  return navigator.mediaDevices.enumerateDevices();
}

function handleError(error) {
  console.log('navigator.MediaDevices.getUserMedia error: ', error.message, error.name);
}

function start() {
  if (window.stream) {
    window.stream.getTracks().forEach(track => {
      track.stop();
    });
  }
  const audioSource = audioInputSelect.value;
  const videoSource = videoSelect.value;
  const constraints = {
    audio: {deviceId: audioSource ? {exact: audioSource} : undefined},
    video: {deviceId: videoSource ? {exact: videoSource} : undefined}
  };
  navigator.mediaDevices.getUserMedia(constraints).then(gotStream).then(gotDevices).catch(handleError);
}

audioInputSelect.onchange = start;
audioOutputSelect.onchange = changeAudioDestination;

videoSelect.onchange = start;

start();

2、index.html文件

<!DOCTYPE html>
<!--
 *  Copyright (c) 2015 The WebRTC project authors. All Rights Reserved.
 *
 *  Use of this source code is governed by a BSD-style license
 *  that can be found in the LICENSE file in the root of the source
 *  tree.
-->
<html>
<head>

    <meta charset="utf-8">
    <meta name="description" content="WebRTC code samples">
    <meta name="viewport" content="width=device-width, user-scalable=yes, initial-scale=1, maximum-scale=1">
    <meta itemprop="description" content="Client-side WebRTC code samples">
    <meta itemprop="image" content="../../../images/webrtc-icon-192x192.png">
    <meta itemprop="name" content="WebRTC code samples">
    <meta name="mobile-web-app-capable" content="yes">
    <meta id="theme-color" name="theme-color" content="#ffffff">

    <base target="_blank">

    <title>Select audio and video sources</title>

    <link rel="icon" sizes="192x192" href="../../../images/webrtc-icon-192x192.png">
    <link href="//fonts.googleapis.com/css?family=Roboto:300,400,500,700" rel="stylesheet" type="text/css">
    <link rel="stylesheet" href="main.css">

    <style>
        div.select {
            display: inline-block;
            margin: 0 0 1em 0;
        }

        p.small {
            font-size: 0.7em;
        }

        label {
            width: 12em;
            display: inline-block;
        }
    </style>

</head>

<body>
<div id="container">

    <h1><a href="//webrtc.github.io/samples/" title="WebRTC samples homepage">WebRTC samples</a><span>Select sources &amp; outputs</span>
    </h1>

    <p>Get available audio, video sources and audio output devices from <code>mediaDevices.enumerateDevices()</code>
        then set the source for <code>getUserMedia()</code> using a <code>deviceId</code> constraint.</p>

    <div class="select">
        <label for="audioSource">Audio input source: </label><select id="audioSource"></select>
    </div>

    <div class="select">
        <label for="audioOutput">Audio output destination: </label><select id="audioOutput"></select>
    </div>

    <div class="select">
        <label for="videoSource">Video source: </label><select id="videoSource"></select>
    </div>

    <video id="video" playsinline autoplay></video>

    <p class="small"><b>Note:</b> If you hear a reverb sound your microphone is picking up the output of your
        speakers/headset, lower the volume and/or move the microphone further away from your speakers/headset.</p>

    <a href="https://github.com/webrtc/samples/tree/gh-pages/src/content/devices/input-output"
       title="View source for this page on GitHub" id="viewSource">View source on GitHub</a>
</div>

<script src="https://webrtc.github.io/adapter/adapter-latest.js"></script>
<script src="main3.js" async></script>

<script src="ga.js"></script>
</body>
</html>